As illustrated in FIG. 1, a conventional driving device of the massaging chair consists of a motor "M" for driving a main shaft 11 on which a bevel gear 12 is mounted such that the bevel gear 12 is engaged with a spiral gear 131 mounted on a rotary shaft 13. A worm rod 14 is mounted on another end of the main shaft 11 for linking a rotary shaft 15 at a lower speed in conjunction with a worm wheel 16 mounted on a rotary shaft 15. Since the rotary shafts 13 and 15 are incapable of synchronous rotation, the transmissions of the bevel gear 12 and the worm rod 14 are brought about by the main shaft 11 in cooperation with a clutch 20. As shown in FIG. 2, the clutch 20 comprises a left locating sleeve 21 and a right locating sleeve 22. The left locating sleeve 21 is provided with two locating holes 211 opposite in location to each other, whereas the right locating sleeve 22 is provided with two locating holes 221 opposite in location to each other. As a result, the locating sleeves 21 and 22 can be located securely on a locating shaft 101 of a main body 10 such that a rotor 23 is rotatably fastened between the two sleeves 21 and 22 in conjunction with two rings 24 which are resistant to wear and heat. The rotor 23 is provided with a spiral hole 231, which is engaged with a spiral rotor 25 which is provided respectively at both ends thereof with an end gear 252 corresponding in location to the end gears 121 and 141 of the bevel gear 12 and the worm rod 14. The spiral rotor 25 is provided at one end thereof with a polygonal hole 251, which is engaged with a polygonal portion of the main shaft 11 such that the spiral rotor 25 is capable of sliding freely on the main shaft 11.
When the motor "M" starts to turn forward to drive the main shaft 11, the spiral rotor 25 is actuated to turn in the spiral hole 231 of the rotor 23 such that the end gear 252 of the spiral rotor 25 moves toward the bevel gear 12. The end gear 252 of the rotor 25 is securely engaged with the end gear 121 of the bevel gear 12. When the spiral rotor 25 is incapable of axial displacement inside the spiral hole 231 of the rotor 23, the rotor 23 and the spiral rotor 25 can be actuated synchronously. When the main shaft 11 is driven to turn backward, the spiral rotor 25 is actuated to displace likewise such that the end gear 252 of the spiral rotor 25 is engaged with the end gear 141 of the worm rod 14. The worm rod 14 and the rotor 23 are thus actuated synchronously by the spiral rotor 25 to turn. With the cooperation of the clutch 20, the main shaft 11 is capable of linking independently the rotary shaft 13 and the rotary shaft 15. In other words, the rotary shafts 13 and 15 are caused to turn at different speeds by the forward rotation and the reverse rotation of the main shaft 11. As a result, when the rotary shaft 13 is turned, the massaging chair is capable of bringing about a kneading effect. On the other hand, when the rotary shaft 15 is turned, the massaging chair brings about a beating effect.
Such a prior art driving device as described above has several shortcomings, which are described explicitly hereinafter.
It is technically difficult to make the rotor 23 and the spiral rotor 25 by a plastic injection molding. Such injection molding is expensive and often results in a high rejection rate of the rotors.
The clutch 20 is composed of many component parts which can not be easily assembled with precision. For example, the locating sleeves 21 and 22 can not be assembled with the locating shaft 101 of the main body 10 with ease and precision.
After a prolonged service, the rotor 23 and the spiral rotor 25 are vulnerable to deformation. In addition, the rotor 23 and the spiral rotor 25 must be lubricated from time to time so as to ensure that they are capable of smooth engagement. Moreover, a mechanical friction can take place between the rotor 23 and the locating sleeve 21 or 22 at such time when the rotor 23 rotates at a high speed along with the spiral rotor 25.